This invention relates to rotatable handgrips for actuating devices used on handlebar-steered vehicles. More particularly, it relates to elongated rotatable handgrips that are readily engaged from an outboard hand position on the handlebar.
Rotatable handgrips are typically used on bicycles to actuate both internal and external gear shifting mechanisms such as hubs and derailleurs, respectively, and on motorcycles to actuate carburetor throttle bodies. On bicycles, thumb and index finger actuated lever-type shifting devices supported on the handlebar are also commonly used. Such lever devices, however, require the removal of one or more fingers from the handgrip in order to operate the levers to shift gears. This, of course, may contribute to the loss of steering control of the bicycle. With the advent of rotatable handgrip shifters or twistshifters, riders are now able to shift gears without releasing their fingers from the handgrip thereby maintaining improved steering control of the bicycle.
Bicycle twistshifters may embody either fill-length rotatable handgrips, similar to motorcycle throttles, or partial-length rotatable handgrips located inboard of stationary grips. One such inboard shift actuator is disclosed in U.S. Pat. No. 4,900,291 issued Feb. 13, 1990 and commonly assigned to SRAM Corporation. Other commonly assigned patents which disclose rotatable shift actuators mounted on a handlebar inboard of stationary handgrips include U.S. Pat. No. 4,938,733 issued Jul. 3, 1990, U.S. Pat. No. 5,102,372 issued Apr. 7, 1992, U.S. Pat. No. 5,197,927 issued Mar. 30, 1993, U.S. Pat. No. 5,564,316 issued Oct. 15, 1996, and U.S. Pat. No. 5,584,213 issued Dec. 17, 1996. A rotatable shifter embodying a full-length handgrip extending to the end of the handlebar is shown in U.S. Pat. No. 2,874,587 issued Feb. 24, 1959.
Twistshifters embodying conventional inboard and full-length rotatable grips, however, do have functional drawbacks. Twistshifters with full-length grips may contribute to loss of rider control due to inadvertent shifts under hard braking or acceleration or from jolts when riding on uneven surfaces. Inboard twistshifters greatly improved rider steering control by allowing stationary grips to be positioned symmetrically outboard of the rotatable grips. This allows the rider to shift the rotatable grip with the inboard fingers while maintaining a secure grip on the stationary grip with the rest of the hand. Nevertheless, conventional inboard twistshifters may be disadvantageous under emergency steering conditions such as when the front wheel of the bicycle hits an obstacle or catches a rut in the terrain. Under such circumstances, the rider instinctively slides his hands to a more stable outboard position on the handlebar for improved steering control, albeit away from the rotatable handgrip. This is an especially common occurrence when riding a mountain bike in off-road conditions where even under non-emergency conditions a rider negotiating the bicycle over rocks and fallen trees will want to shift his hands further outboard to maintain better steering control. Bar ends, secured to the outboard ends of handlebars and commonly used on mountain bikes, provide convenient stops when shifting the hands outwardly or away from the frame of the bicycle. In doing so, quite often the rider temporarily looses the ability to shift gears and must wait till the end of the maneuver before first repositioning his hands inboard over the rotatable grip and then shifting into the proper gear. This results in a potentially dangerous riding situation where the rider is forced to negotiate an obstacle in the wrong gear or, even worse, attempts to both slide his hands inboard and shift gears during the maneuver itself. Accordingly, this unnecessary risk can be eliminated by providing the rider with the ability to shift gears effectively and instinctively regardless of the rider""s hand position on the handlebar and in all riding situations.
It is an object of this invention to provide a rotatable handgrip that permits a rider to readily actuate a control mechanism from a more outboard hand position on the gripping surface of a handlebar. It is another object of this invention to provide a rotatable handgrip that is readily engaged from any hand position on the gripping surface of the handlebar.
In accordance with this invention, an actuating device including an elongated rotatable grip is provided that sufficiently extends further outboard toward the end of the handlebar to permit a rider to actuate a response mechanism with his hands positioned further outboard on the handlebar.
According to another aspect of the invention, a hand rotatable grip for mounting on a handlebar having a longitudinal axis includes a body having a first region with a first radius, and adapted to be grasped by an index finger of a rider. A second region adjoining the first region has a second radius greater than the first radius and is adapted to be grasped by a middle finger of the rider""s hand. A third region of the body adjoining an outboard end of the second region has a third radius less than the second radius, and is adaptable to be grasped by the ring and little fingers of a rider""s hand. This grip forms an ergonomic torque-transmitting surface for all of the digits of a rider""s hand.